This invention relates generally to dock levelers and, more particularly, to dock levelers having end barrier structures.
Dock levelers are typically installed in the loading dock areas of factories, warehouses and similar facilities. In use, a dock leveler serves primarily as a ramp or bridge that extends from the loading dock area of the factory or warehouse into the rear end of a mack trailer. Truck trailers, however, are not of perfectly uniform height above ground. Furthermore, the actual height of a mack trailer above ground varies as the trailer is loaded and unloaded. Accordingly, dock levelers are arranged to pivot both upwardly and downwardly relative to the loading dock floor in order to accommodate trailers of different heights.
When not in use, dock levelers are typically positioned level with the floor of the loading dock area. This helps avoid the creation of trip hazards and permits fork trucks and other vehicles to be driven across the loading dock floor. Nevertheless, a potential hazard still exists in that vehicles can inadvertently drive off the ends of the dock levelers into the adjacent drive approach. To avoid this hazard, a variety of mechanisms have been proposed.
In one mechanism, a pivoting plate was affixed to the end of the dock leveler. When the dock leveler was in use, the plate was pivoted to a substantially horizontal position substantially coplanar with the top surface of the dock. When the dock leveler was not in use, the plate was pivoted to a substantially vertical position to form a barrier to keep vehicles from falling off the end of the dock leveler. Although effective, the system created a pinch hazard as the plate pivoted between the vertical and horizontal positions.
In another system, such as that shown in U.S. Pat. No. 4,920,598, a lip, hingedly connected to the front edge of the dock leveler, was arranged to slide vertically between a first position wherein a portion of the lip protruded above the ramp and a second position wherein no portion of the lip extended above the ramp. In the first position, the protruding portion of the lip formed a barrier to keep vehicles from running off the end of the dock leveler.
In still another system, such as that shown in U.S. Pat. No. 5,040,258, a dock leveler included a lip that was operatively connected to the front edge portion of the dock leveler ramp for movement between a depending position and an outwardly extended cantilevered position. A barrier assembly connected to the lip was arranged to project above the ramp surface when the lip was in the depending position to form a barrier when the lip was not extended.
Although each of these systems was effective in keeping vehicles from running off the end of the ramp, none of these systems was effective in preventing vehicle damage to the overhead doors of the loading dock, which can occur, for example, when the overhead doors of a loading dock are closed and a fork truck or other vehicle moving on the upper ramp surface of an idle dock leveler collides with the closed door. Although the closed door keeps the vehicle from running off the end of the dock leveler, the door itself frequently suffers considerable damage in the resulting collision. Although such door damage is preferable to the potentially far more serious damage and injury that can result if the vehicle were to drive off the end of the dock leveler, door repair can, in time, become a significant expense.